Use of AOVs for Ventilation Purposes

[Geoff]

Morning chaps and chappesses,

I have small query regarding AOVs and their use as a means of ventilation in hot weather.

I've got an extra care scheme that has been using the AOVs at the end of the corridors to provide a natural means of ventilation during hot weather. At build they were supposed to be designed to facilitate this but as can happen during a design and build project it was changed by someone (no records available to say who it was) and the motors on some of them have burnt out. They have obviously been repaired but I'm concerned that it will happen again and there are no mechanical means of providing the ventilation.

We are going through the process of getting this treated as a latent defect/design flaw, etc, and the contractor has come back stating that the regs are changing to say that AOVs cannot be used for this prupose. I doubt that it is a change to legislation but  thought it might be one of the many shandards that are out there that has been reviewed; I'm  not aware of that proposed or actual change so I thought I'd ask the wise heads in here, if such a thing is in the offing?

Geoff

[kurnal]

In my experience use of AOVs in this way is becoming increasingly common due to other environmental factors- insulation etc. I have seen many with a complex automatic control system incorporating heat sensors for automatic ambient temperature control, whilst fire performance is controlled by smoke detectors in the conventional way. I am not aware of any changes to codes of pracice preventing this but a quick check with BSI online will show if the standards are currently under review.
I guess that siting of smoke detectors becomes more important if all vents into a smoke shaft are simultaneously open - the detector within 1.5m of the shaft becomes more important- and perhaps smoke detectors in the staircase , often omitted in AOV schemes might become more relevant. The overriding rule is that on operation of a yellow BGU or smoke detector the system must revert to fire mode - the all vents close except those on the fire floor and the vents at the head of the shaft and staircase in accordance with the fire design C&E.

[wee brian]

If its an AOV to outside air, does it cause a problem?

[kurnal]

I guess if it works in conjunction with the vent in the staircase then this needs to be a consideration for ambient ventilation.

[Fishy]

The fire safety kit will probably have been designed with a 'required duty' based upon the relevant safety-related testing regime and very infrequent 'real' activations, so entirely foreseeable that frequent operation for 'comfort' ventilation could cause failure.  Motorised fire dampers tend to suffer similar failures if frequently operated. 

With regard to the original question - nothing to stop you doing it, so far as I know, but if one wanted to use the vents in this way either drive them open and leave them open until the weather gets colder, or I'd suggest either an enhanced maintenance regime (which might actually burn out the motors more quickly, but at least you'll know they're busted) or a discussion with the manufacturers about whether they have a more robust product?